HP BL680c HP local I/O technology for ProLiant and BladeSystem servers - Page 8

The PCI Express specification also defines two other PCI-like form factors. A PCI Express Mini Card, similar to the Mini PCI card will include a x1 connector for use in portable products. The ExpressCard is similar to PCMCIA cards and will include a x1 PCI Express connector and a USB 2.0 connector for use in desktop and portable products (Figure 8). Figure 8. PCI Express Mini Card (left) and ExpressCard (right) form factors PCI Express card interoperability The PCI Express specification provides for significant interoperability features between PCI Express add-in cards and slots. Up-plugging (for example, a x4 card into a x8 slot) is supported. Additionally, the specification also supports down-shifting, which allows the creation of slots with larger physical connectors that are wired for a smaller logical link to the server's I/O hub. For best performance, of course, a card should be used in a slot that supports its logical link size; however the availability of down-shifted slots provides the flexibility to use larger cards (for example, x8) in slots with smaller logical links if necessary. Table 1. PCI Express add-in card interoperability x4 Connector x4 Link x8 Connector x4 Link x8 Connector x8 Link x16 Connector x8 Link x16 Connector x16 Link x4 Card x4 Operation x8 Card Not Allowed x16 Card Not Allowed x4 Operation x4 Operation Not Allowed x4 Operation x8 Operation Not Allowed x4 Operation x8 Operation x8 Operation x4 Operation x8 Operation x16 Operation It is HP's design philosophy to provide larger connectors whenever possible. Most slots with x4 links have x8 connectors and slots with x8 links come with x16 connectors, thus delivering maximum flexibility. Connector and link width for the slots should be documented on the hood label of each ProLiant server. 75 Watt and 150 Watt PCI Express slots In general, the PCI Express specification calls for slots to support up to 25-watt power consumption for each add-in card. In order to support the emerging high performance add-in cards that consume more than 25 watts of power, the specification also supports the concept of a 75-watt slot. Slots rated for 75 watts are distinguishable from others by the required increase in spacing around them which is needed to dissipate the additional heat associated with the higher power consumption. 8